Breast cancer is one of the most pernicious diseases in women. This disease, which is the most common cancer of women and which now attacks one woman in thirteen, has had a stationary death rate for forth years in spite of advances in surgical techniques, radiotherapy and chemotherapy. In fact, of one considers that one-third of women present themselves with inoperable breast cancer, only 25% or less of women with breast cancer are alive and well ten years after diagnosis.
The probability of primary prevention of the disease by a vaccine or by environmental control, such as change in nutrition, is poor for the immediate future. The outlook for a wonder drug or other remedy to cure the disease at any stage is not promising. It is known however, that our present methods of surgery, radiotherapy, and chemotherapy are effective for long-term survival if applied when the disease is localized to the breast. Since many of the breast cancer cases are not localized when first seen by the clinician, a means must be found to have women present themselves for examination with their disease at an earlier stage than is commonly the case. This means in a practical way, detection of preclinical cancer is apparently "well" women, when the disease is unsuspected by patient or physician, as is the case in mass screening.
The effectiveness of mass screening is illustrated by the one-third reduction in mortality achieved in the large-scale screening program for breast cancer detection conducted by the Health Insurance Plan of Greater New York, under contract with the National Cancer Institute. (The Guttman Breast Diagnostic Institute in New York has conducted this project and most of the basic statistical information given here is taken from Prof. Strax, the head of the Institute).
On initial examination, the number of prevalent cancers present is high, depending on such factors as self-selection and age of women. Because cancers have been present for varying lengths of time, only half of the cancers are free of nodal involvement. On subsequent examination, the number of interval cancers, which have become detectable since the previous examination, is much less, but the majority have no nodal spread.
There are usually two steps in the diagnosis of breast cancer. First the detection of a lesion by a screening method, (or symptom like pain) and then narrowing down the diagnosis, first by non invasive methods and finally by biopsy, which when positive, is mostly followed by immediate surgical removal of the breast. Such factors as time of examination, radiation dose or cost of the study assume minor roles when evaluating a lesion which has already been detected.
In screening for breast cancer, however, large numbers of women are involved in a program who presumably have no disease or have only minimal symptoms. These women would not be having the examinations were it not for the opportunity offered by the screening program. The major thrust in screening is not, therefore, differential diagnosis of a lesion, but the step preceding that--detection of an abnormality. All one does in mass screening must be directed to the following objective: the initial detection of an abnormality in the simplest, safest, most accurate and most economical manner possible. The information gathered must then be passed along to the women's medical adviser for him to proceed to a differential diagnosis on the way to proper treatment.
At present the following methods are used for the detection of breast cancer in most clinics: (1) Clinical examination including: a. Manual palpation, b. Appearance of the skin, c. Deformation of the breast; (2) X-rays (there are several variants available); (3) Thermography.
None of these methods is satisfactory by itself, neither are combinations of these methods fully satisfactory. Cancerous tumors are detected in most cases when several years old. It should also be added that final and reliable diagnosis is only done by biopsy. In many institutions positive diagnosis is obtained in only 25% of biopsies done. It seems therefore obvious that better physical methods for screening of a large number of patients as well as more reliable diagnosis before biopsy would be very important. The present technology and the large number of patients involved make computer aided devices methods of choice.
Of the presently used methods only thermography lends itself to computerized automation. A project in that field has been conducted by Prof. Anliker at the E.T.H. Zurich. Success is limited by the rather small number of tumors that cause rise in temperature of the skin. For several years a group at the Massachusetts Institute of Technology has been trying to use microwave emission in an analogous way. This would allow finding deeper-lying temperature changes. But difficult signal-to-noise problems allow only measurements of a few points in a reasonable time.
In a thesis entitled Measurement Errors and Origin of Electrical Impedance Chages in the Limb by David Keith Swanson at the University of Wisconsin-Madison, at Chapter IX there is a discussion of an impedance camera employing a multi-element probe for performing measurements of the thorax. Operation at swept frequencies is suggested. There is no disclosure of a swept frequency apparatus of this type nor of the importance of the rate of change of conductance or capacitance as a function of frequency as providing information independent of extraneous factors.